A pumping arrangement of this kind is disclosed in U.S. Pat. No. 4,157,092. This pumping arrangement pumps breathing gas into the breathing circuit of a ventilating apparatus. The pumping arrangement includes a piston-cylinder unit which is insertable into the housing of the ventilating apparatus and can again be removed therefrom. The base plate of the piston carries annular inserts of ferromagnetic material which serve as a coupling aid and which are contacted and rigidly held by permanent magnets. These magnets are accommodated in a disc which is attached to a motion actuator which is configured as a displacement rod connected to a drive unit. The magnets take the piston along during the pumping strokes and thereby transmit the pump strokes for the breathing gas. Connecting lines are fixedly connected to the piston-cylinder unit for leading the breathing gas into and out of the pumping arrangement.
In the known pumping arrangement, the piston-cylinder unit can be removed during the operation of the drive unit or it can self-loosen whereby unwanted operational disturbances can occur. For removal, additional manipulation is required for loosening the gas lines. The piston is not fixed when the piston-cylinder unit is removed. Uncontrolled displacements occurring during manipulation can lead to damage or prevent a later coupling.